1. Field of the Invention
The invention concerns a process for filling a liquid crystal cell with a liquid crystal material.
2. Description of the Prior Art
Liquid crystal material is generally a mixture of different liquid crystal substances. It should be noted that for the sake of brevity, liquid crystal cells hereinafter will be referred to to cells.
Various processes for filling cells with liquid crystal material are known. A first process involves lowering an evacuated cell until it is immersed in liquid crystal material in a container inside the vacuum jar. The vacuum jar is then slowly aerated, whereby the liquid crystal material is forced into the cell interior. The speed of aeration is dependent on the viscosity of the liquid crystal material. A too rapid influx of the material must be avoided because this could result in a change in the orientation properties of orientation layers or spacers could be flushed out of position. On the other hand, the inflow speed should not be too low because of the need to obtain a sufficiently high production output. It is therefore common to heat liquid crystal material of high viscosity, e.g. ferroelectric or smectic material so that it flows sufficiently quickly through the filling hole into the cell interior.
According to another process, the filling hold, pointing upwards, of a cell is supplied with liquid crystal material. Aeration is quickly performed, the cell is removed from the vacuum, placed in an over and its filling hold is connected with a reservoir of liquid crystal material.
According to a third process, a liquid crystal cell is placed with its filling hold upwards in a vacuum jar. The filling hole is supplied with a quantity of liquid crystal material sufficient to fill the whole cell interior. The vacuum jar is then slowly aerated so that filling can occur.